Body temperature changes such as the one you described is common in people with the flu. Fevers develop when the body's immune system releases molecules known as pyrogens into the blood. These cause the body's thermostat (the hypothalamus) to raise the body temperature. These pyrogens only last in the blood for a short time. If the immune system stops making them, the body temperature will fall back to normal.
As for the rest of you boyfriend's symptoms, they do sound like the flu. Coughing, sneezing, and muscle aches are all common. However, high fevers like the one you described can also occur with bacterial infections. It is possible that the symptoms you described could be pneumonia, though it is less likely. This is important because pneumonia is treated with antibiotics whereas the flu is typically only treated in people with a lot of other health problems.
I suggest that your boyfriend schedule an appointment with his primary care physician
. He or she can take a more detailed history of his symptoms and take a close look at him including a thorough lung exam. His doctor
may even have him get a chest x-ray
to rule out the possibility of pneumonia. I hope he feels better.